The Sliding Filament Theory The Sliding Filament Theory

The Sliding Filament Theory

The Sliding Filament Theory Troponin complex

The Sliding Filament Theory

REVIEW: Cycle The Contraction

So how was it figured out how muscle fibers contract? Sliding Filament Theory article & Concept Map - As you read the article that tells you experiments that led closer to day skeletal muscle, be about the first scientists the presentunderstanding of looking for…

5 Golden Rules of Skeletal Muscle Activity

Muscles & Body Movements • Movement is attained due to a muscle moving an attached bone • Muscles are attached to at least 2 points • Origin • Attachment to moveable bone • Insertion • Attachment to immovable bone

Isotonic Contractions • Isotonic Contraction: • Example: lifting dumbbells with arm • Tension (effort) increases & muscle fibers shorten & lengthen • Concentric contraction: • Tension (effort) exceeds resistance (weight) & muscle shortens • Eccentric contraction: “iso” – same “ton” – weight/resistance • Resistance exceeds tension (effort) & muscle lengthens (due to gravity)

Isometric Contractions • Isometric Contraction: • Example: pushing against a wall • Tension (effort) never exceeds resistance (weight) • Muscle does NOT change length “iso” – same “metr” – distance

Muscle Relaxation • Relaxation of muscle fibers • Passive process • Combo of elastic forces, opposing muscle contractions & gravity to elongate a contracted muscle • Elastic force: some energy used to stretch tendons in contraction phase forces a recoil • Opposing muscle contractions: muscles move in antagonistic pairs • Gravity: pulls down muscle to extended position

Rigor mortis Within 3 -4 hours after death • Dying muscle cell membranes become more permeable to Ca+ ions • Promotes myosin cross-bridge binding • After death, circulation of nutrients ends • Without ATP, Ca+ ions are not removed & crossbridges cannot detach from actin sites so muscles become locked in place – “stiff” • Rigor mortis disappears as muscle proteins break down several hours after death (48 -60 hours)

Effect of Exercise on Muscles • Exercise increases muscle size, strength & endurance • Aerobic (endurance/ cardiovascular) exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue • Makes body metabolism more efficient • Improves digestion & coordination • Resistance (isotonic & isometric) exercise (weight-lifting) increases muscle size & strength

Fast vs. Slow-Twitch Muscles • Fast Twitch Fibers • Most skeletal muscle fibers • Contract in 0. 01 sec or less after stimulation • Large in diameter • Contain densely-packed myofibrils • Have large glycogen reserves & few mitochondria • Produce powerful contractions • Fatigue rapidly • “white muscle fibers”

Fast vs. Slow-Twitch Muscles • Slow Twitch Fibers • ~Half the diameter of fast fibers • Take 3 x as long to contract after stimulation • Specialized to continue contracting for extended periods • Contain extensive network of capillaries & has higher oxygen supply • Contain red pigment myoglobin • Contain more mitochondria than fast fibers • “red muscle fibers” • Intermediate Fibers • Contain properties of fast fibers & slow fibers

Tetanus • Many toxins, drugs & diseases may interfere with events occurring at the neuromuscular junction • Tetanus: infection of Nervous System from potentially deadly bacteria Clostridium tetani – Bacteria spreads & makes poison called tetanospasmin – Poison blocks nerve signals from spinal cord to skeletal muscles, causing severe muscle spasms – Prolonged muscle contractions, spasms & stiffness – Spasms can be so powerful that they tear the muscles or cause fractures of the spine